Glutaminolysis is the metabolic process of glutamine, aberration of which has been implicated in several pathogeneses. Although we and others recently found a diversity of metabolic dysregulation in organ fibrosis, it is unknown if glutaminolysis regulates the profibrotic activities of myofibroblasts, the primary effector in this pathology. In this study, we found that lung myofibroblasts demonstrated significantly augmented glutaminolysis that was mediated by elevated glutaminase 1 (Gls1). Inhibition of glutaminolysis by specific Gls1 inhibitors CB-839 and BPTES as well as Gls1 siRNA blunted the expression of collagens but not that of fibronectin, elastin, or myofibroblastic marker smooth muscle actin-α. We found that glutaminolysis enhanced collagen translation and stability, which were mediated by glutaminolysis-dependent mTOR complex 1 activation and collagen proline hydroxylation, respectively. Furthermore, we found that the amount of the glutaminolytic end product α-ketoglutarate (α-KG) was increased in myofibroblasts. Similar to glutaminolysis, α-KG activated mTOR complex 1 and promoted the expression of collagens but not of fibronectin, elastin, or smooth muscle actin-α. α-KG also remarkably inhibited collagen degradation in fibroblasts. Taken together, our studies identified a previously unrecognized mechanism by which a major metabolic program regulates the exuberant production of collagens in myofibroblasts and suggest that glutaminolysis is a novel therapeutic target for treating organ fibrosis, including idiopathic pulmonary fibrosis.

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Profound impairment in cellular oxygen consumption, named cytopathic dysoxia, is one of the pathological hallmarks in the lungs of patients with pathogen-induced acute lung injury (ALI). However, the underlying mechanism for this functional defect remains largely unexplored. In this study, we found that primary mouse alveolar epithelial cells (AECs) conducted robust fatty acid oxidation (FAO). More importantly, FAO was strikingly impaired in AECs of mice with lipopolysaccharide (LPS) induced ALI. The metabolic deficiency in these cells was likely due to decreased expression of key mediators involved in FAO and mitochondrial bioenergenesis, such as PGC-1α, CPT1A and MCAD. We found that treatment of alveolar epithelial line MLE-12 cells with bronchoalveolar lavage fluids (BALFs) from mice with ALI decreased FAO and this effect was largely replicated in MLE-12 cells treated with pro-inflammatory cytokine TNF-α, which was consistent with downregulations of PGC-1α, CPT1A, LCAD and MCAD in the same treated cells. Furthermore, we found that the BALFs from ALI mice and TNF-α inhibited MLE-12 bioenergenesis and promoted cell apoptosis. In delineation of the role of FAO in ALI in vivo, we found that conditional ablation of AEC PGC-1α aggravated LPS induced ALI. In contrast, fenofibrate, an activator of the PPAR-α/ PGC-1α cascade, protected mice from this pathology. In summary, these data suggest that FAO is essential to AEC bioenergenesis and functional homeostasis. This study also indicates that FAO impairment induced AEC dysfunction is an important contributing factor to the pathogenesis of ALI.